I have the original P180, and until after some recent upgrades, had never had cooling issues. I'm in the process of modding some areas for better cable management and airflow but am trying to find the VGA duct that came with the 180B. I just installed a Gelid Icy Vision on my GTX 260 but it blows down and I'd like to use the VGA duct in an exhaust config since the rear 120mm fan in the P180 will not be pulling the heated air off the card and out the back. I have not seen it for sale or replacement on Antec but am trying to find anyone who had it and doesn't use/want it since the general consensus in the community was to remove and discard it.
I wouldn't bother with it IMO. I tried something similar with a Lian Li VGA duct for my P182, and it actually raised GPU temps rather than lowering them.
What I found to be more effective was to just let the GPU heat rise as it desired, and have two exhaust fans in place (one in the rear, one in the top). I then modified the top spoiler to have it block noise. The mesh in the spoiler comes off easily with its folded metal tabs, and then I inserted a piece of cardboard, and stuck a sheet of thin acoustic foam on the underside. Though thin and cheap, it made a big difference to the apparent level of noise coming out of the top vent.
See my thread here for more ideas: viewtopic.php?f=14&t=63926
The top spoiler mod is in the first post, and scroll down to the second post to see the VGA duct.